The present invention relates to an apparatus for cleaning dust and other surface particulate contaminants from material in sheet form.
There are many applications employing material in sheet form in various processes. For example, in the fabrication of printed circuit boards, the boards are in sheet form, and typically must be cleaned prior to processing steps for defining circuit traces. A trend in the printed circuit board industry is toward increasing use of fine line printed wiring boards. Any small dirt particle can cause a defect, e.g., a short or open circuit. Thus, typically, layers of copper are formed on the outer surfaces of the circuit board, and the fine line circuit traces are defined by photolithographic processes. An intermediate step is the deposit of layers of photoresist material onto the copper layers. Outer thin layers of polyester, e.g., 0.001 inches in thickness are often laid over the photoresist to provide protection during intermediate processing. The photoresist layers may be exposed through the protective layers and a mask which defines the wiring pattern. Subsequent processing includes developing the photoresist. The outer surfaces of the polyester film are typically cleaned to remove dust and other foreign particles, which could otherwise interfere with such steps as the exposure of the photoresist. However, care must be taken to keep from removing the thin polyester films during the cleaning.
U.S. Pat. No. 4,009,047 describes an exemplary device for cleaning sheets, wherein a cleaning roller having a tacky surface is used to pickup dirts particles from a sheet. The device includes a sheet cleaning roller having a higher surface tack than the cleaning roller, to remove the dirt particles from the cleaning roller. The device is relatively complex and expensive to manufacture, and would tend to remove protective thin films as used to protect printed circuit boards during fabrication.